The present research seeks to document the relationship between body temperature and death feigning duration. It is hypothesized that the termination of death feigning, an antipredator behavior, reflects the behavioral solution to challenges to thermal homeostasis. As such, it is expected that ontogenetic changes in the duration of death feigning will reflect the increasing efficiency with which chicks achieve physiological thermoregulatory control over the first three posthatch weeks. Animals will be fed diets with either protien deficits or protien surfeits for three weeks posthatch and given either access to running wheels continuously during this time, or no access. A control group will receive a diet with adequate protein. and either activity access or no access. The deviant diets produce differences in body temperature which exceed or fall below temperatures of normally nourished animals, and they also differentially affect activity and growth. The low protein diet has been shown previously to attenuate death feigning duration relative to an adequate-protein diet. The interactions between diet and activity will be assessed in terms of their effects on body temperature and the duration of death feigning at different points in ontogeny. The procedure will be repeated in two ambient rearing temperatures and with chicks subjected to acute (cloacal probe insertion) and chronic (implantation of temperature telemetry device) methods of body temperature measurement. Death feigning will involve simulated predation by the experimenter. It is anticipated that these manipulations will create different thermoregulatory problems for the various experimental groups and that the solutions to these problems will be reflected in the duration of death feigning.